Stress corrosion cracking electrochemical techniques

Electrochemical noise A variety of related techniques are now available to monitor localized corrosion. No external polarization of the corroding metal is required, but the electrical noise on the corrosion potential of the metal is monitored and analyzed. Signatures characteristic of pit initiation, crevice corrosion and some forms of stress corrosion cracking is obtained. 

WILLIAM H. SMYRL is Professor of Chemical Engineering and Materials Sciences and Associate Director of the Center for Corrosion Research at the University of Minnesota. He received his Ph.D. (chemistry) at the University of California, Berkeley, and spent 3 years at the Boeing Scientific Research Laboratories and 11 years at Sandia National Laboratories. He joined the faculty of the University of Minnesota in 1984. His research interests are modeling of corrosion processes, in situ techniques for metal-metal oxide interface studies, digital impedance for faradaic analysis, stress corrosion cracking, polymer-metal interfaces, and electrochemical processes. 

Localized corrosion and stress corrosion may often be observed. Stress corrosion cracks usually initiate at pits in many systems. The role of pitting is to disrupt films that otherwise prevent the ingress of hydrogen (118, 119). Electrochemical polarization technique may be used to distinguish between SCC and HE mechanisms in high-strength steels in sodium chloride solutions (120). 

The non-electrochemical techniques include direct immersion of materials samples in the test fluid in either the laboratory or plant. These s lmples sometimes have an artificial crevice generated with a serrated washer. They may be welded to determine the effects of welds and weld heat affected zones. Real-time information can be obtained using electrical resistance probes. Heat transfer effects can be evaluated by having a test sample that is exposed to the corrodent on one side and the other side heated or cooled. Stressed samples are used to evaluate stress corrosion cracking tendencies [33]. 

Standard Test Method for Determining Stress-Corrosion Cracking Resistance of Heat-Treatable Aluminum Alloy Products Using Breaking Load Method Standard Practice for Evaluation of Hydrogen UptEike, Permeation, and Transport in Metals by an Electrochemical Technique... 

Comparison of stress corrosion cracking susceptibility of thermally-sensitised and proton-irradiated 304 stainless steel using electrochemical noise techniques Journal of Nuclear Materials 258-283 (Part B), Oct. 1998, S. 2046-2053... 

Returning now to stress corrosion cracking, it is evident that it is premature to expect calculation of the ECP in the coolant circuit. Of a SCWNPP, but it is possible to perform experiments under electrochemical control using the electrochemical techniques (reference electrodes, etc.) discussed above. However, none of the work reported to date has employed a reference electrode to moni-... 

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